Ignition apparatus and method of making same



s p 1953 H. A. BRINSON ET AL 2,651,298

IGNITION APPARATUS AND METHOD OF MAKING SAME Filed D90- 26, 1947 J 30 24 r m; mun-W4 I I -25 Z 2 1 2 1 J32 16' "J15 i w 7 :FLUX 7 J 3 -11 j 20 1 l INVENTORS.

JAM 5. 6% BY flazbdfjm ATTORNEY.

Patented Sept. 8, 1953 IGNITION APPARATUS AND METHOD OF MAKING SAlIE Harry A. Brinson, Sidney, and Thomas G. Brady, Oneonta, N. Y., assignors to Bendix Aviation Corporation, New York, N. Y., a corporation of Delaware Application December 26, 1947, Serial No. 793,782

14 Claims. (Cl. 123-169) This invention relates to electrical apparatus and more particularly to spark producing means adapted for use in igniting combustible gases such as in combustion engines.

One of the objects of the present invention is to provide a novel igniter plug which is adapted for use in starting and maintaining combustion in engines of the type employed for jet propulsion of aircraft and the like.

Another object of the invention is to provide an igniter or spark plug of the above type embodying a novel center or insulated electrode assembly.

Still another object is to provide a radio shielded spark plug wherein the insulated center electrode assembly is supported in a metallic shell in a novel manner.

A further object is to provide a novel igniter plug of the radio shielded type which may be simply and inexpensively constructed from a very small number of parts and which is sturdy in structure and efiicient in operation.

Another object is to provide a device of the above type which is so constructed as to facilitate assembly of the parts and assure gas tight joints therebetween.

The above and further objects and novel features of the invention will more fully appear from the following detailed description when the same is read in connection with the accompanying drawing. It is to be expressly understood, however, that the drawing is for the purpose of illustration only and is not intended as a definition of the limits of the invention.

The single figure of the drawing is a vertical section, with parts broken away, of one form of igniter plug and terminal connector therefor embodying the invention.

The novel center electrode assembly of the illustrated structure comprises a rigid tubular insulator 5 having a stepped bore 6, 1, 8 therethrough. Extending through and closely fitting the reduced bore 6 is an electrode bar or rod 9 which has an intermediate enlarged portion or collar I0 that is only slightly smaller in diameter than the bore 1 and engages the tapered internal shoulder I l in the insulator. The uppermost end of bar 9, as viewed in the drawing, is appreciably smaller in diameter than bore 1 to provide an annular space for a sealing compound I2 and is countersunk to form a recess for receiving the end of a small wire conductor I 4.

The conducting portion of the electrode assembly is completed by a terminal [5 which is positioned in insulator 5 by the enlarged head portion thereof engaging the shoulder [6 at the inner end of bore 8. The inner end of terminal I5 is of a somewhat smaller diameter than bore 8 and has a countersunk recess for receiving the other end of wire [4. The latter is preferably a molybdenum wire but other types of metal may be employed. In order to insure good electrical contact and thereby avoid any electrical burning of the assembled parts, each end of wire [4 is preferably soldered in its recess, such as by means of silver solder H. A good low resistance connection is thus provided, making the structure adaptable for use in a circuit in which high currents flow during operation. The central longitudinal portion of terminal I5 may be slightly undercut to provide a locking engagement with the filling or sealing compound [8 to be next described.

The space within bore 1 around the metallic conducting parts is preferably filled with nonconducting sealing compounds which seal the bore against the leakage of gases and which tend to block the conduction of heat toward the outer or upper end of the center electrode assembly. The bottom or inner portion of the bore around the upper end of electrode bar 9 is preferably filled with a fused mixture l2 of lead oxide (one part by weight) and aluminum oxide (4 parts). The remainder of the filling compound may preferably consist of a fused mixture I8 of lead oxide (1 part) and Pyrex or borosilicate glass (3 parts). As will hereinafter appear, these compounds are inserted in the bore in powdered or pulverized form and thereafter fused to form a rigid mass. The mixture I2 has a melting or softening point which is somewhat higher than that of compound 18 so that the former will not become sufficiently fluid to flow into the clearance space between bore 6 and rod 9 when the latter compound is heated during assembly to a temperature which will assure a good seal as hereinafter described.

In assembling the above described parts, the ends of wire 4 are first soldered into the recesses in the adjacent ends of terminal I 5 and electrode bar 9, a sufficient length of wire being used to permit withdrawal of terminal IS without disturbing the position of bar 9. A small portion of bore 8 is then filled with a quantity of powdered filling material l2, the latter being packed in by vibration or other suitable means. The remainder of bore 1 is then filled with a quantity of the powdered compound l8. Thereafter, while pressing terminal l5 into the bore under a constant pressure of from 50 to 60 pounds, the entire assembly is uniformly heated by flames, electrical induction or the like. The application of heat should be gradual and at such a rate as to permit the seating of the head of terminal I 5 against shoulder l6 within an elapsed time of two to three minutes. It will be understood that the powdered compounds must be subjected to a suiflciently high temperature to cause the lead oxide content thereof to soften or melt and thus create a flowable mass which will permit the insertion of terminal l5 and then set to a solid non-porous mass which completely fills bore 1 around the small wire [4. When the terminal has been seated, the pressure should be maintained thereon while the assembly is permitted to cool for a minute or more. Preferably, the compounds reach a temperature of about 1500 F. Since the aluminum oxide content of mixture [2 has a higher melting point than the borosilicate glass of compound l8, the former will not become as fluid as the latter and, hence, will prevent any flow beyond shoulder H toward the nose of the plug.

The above-described center electrode assembly is supported in and radio shielded by a tubular shell to the lower end of which is welded a ground electrode 2! for cooperation with the projecting end of electrode bar 9. In order to provide maximum assurance against flash-overs between the terminal l5 and the shell, insulator 5 extends well beyond said terminal and is provided with the enlarged bore 8 to receive a removable connector plug from a source of high voltage energy. For the purpose of conserving space and maintaining the size of the structure as small as possible, the shell 20 is made to closely surround the enlarged portion of the insulator and the latter is supported in the shell in a novel manner to be next described.

In the illustrated embodiment, a portion of the internal wall of shell 2t intermediate the ends thereof is tapered, the larger diameter being next the bottom, as viewed in the drawing. This tapered portion of the shell surrounds a substantially cylindrical portion of insulator 5 and the annular space therebetween is filled with a metallic bushing 22, such as copper, which becomes pliable when heated. To provide assurance against gas leakage and relative movement of the parts, a suitable flux, such as powdered borax may be incorporated in the joint between the surfaces of bushing 22 and the engaging surfaces of the shell and insulator.

The assembly of the shell and the insulated electrode assembly in the preferred manner may be effected by first coating the surface of bushing 22. with a flux and dropping it into the shell, the latter being in inverted position. The center electrode assembly is then positioned in the shell b means of a suitable fixture which will hold the shell and electrode assembly in predetermined relative positions while pressure is applied to the bushing. The shell area around the bushing is then heated to a dull red and simultaneously a pressure of about 3,000 pounds is applied 33 intermediate its ends.

by means of a suitable cylindrical tube to the large end of the bushing to wedge it tightly into place between the shell and the insulator. The flux coating on the bushing serves, when thus heated, as a lubricant which greatly facilitates proper assembly of the parts. Also, the melted flux penetrates the pores or interstices of the metal and ceramic surfaces and forms a glaze which insures a gas tight joint during normal usage. The assembly should be allowed to cool for a minute or more before the pressure on the bushing is released. Any residue of flux should be washed off with hot water or other cleansing medium.

A flange 24 may be welded or otherwise suitably secured to shell 20 for use in securing the latter to an engine. If desired, the flange may be integral with the shell.

High voltage electrical energy may be supplied to terminal l5 for eflecting arcing across the gap between electrodes 9 and El through an insulated conductor 25 which is preferably surrounded by a flexible metallic conduit 25. The latter is detachably secured to shell 25 by means of a ferrule 21 soldered to the conduit and a nut 23 threaded onto the shell. Surrounding conductor 25 within bore 8 and the upper end of shell 20 are a rigid insulating sleeve 20 and a flexible sleeve 30 of heat resisting insulating material, such as synthetic rubber. A metallic ferrule 3| may be imbedded in sleeve 29 in the manner illustrated and conductor 25 may be electrically and mechanically connected thereto, as by solder. The ferrule also supports a coil spring 32 which makes contact with terminal l5 when the parts are in assembled relation.

Flexible sleeve 39 extends outwardly into conduit 25 and is provided with an annular flange When the parts are assembled, the lower face of flange 33 is resiliently held in firm contact with the upper end of insulator 5 by means of a spring 34 interposed between ferrule 21 and the upper surface of flange 33. A bevelled metallic washer 35 is preferably seated on flange 33 for engagement by the spring to thereb prevent unnecessary wear. By means of this structure the probability of flash-overs occurring between the high tension conductor or terminal [5 and the grounded shell 20 is reduced to a minimum.

There is thus provided an igniter plug which is novelly fabricated in a novel manner from a small number of relatively simple parts which may be readily and inexpensively assembled. The invention also comprehends a novel center electrode assembly and novel means for supporting the same in a grounded radio shielding shell. Means are also provided in novel combination with said igniter plug whereby the danger of flash-overs and loss of efiiciency thereby is substantially eliminated under all conditions of pressure and humidity.

Although only a single embodiment of the invention is illustrated in the accompanying drawing and described in detail in the foregoing specification, it is to beexpressly understood that the invention is not limited thereto. Materials other than those specifically mentioned may be employed and various changes may be made in the design and arrangementof the parts illustrated without departing from the spirit and scope of the invention.

What is claimed is:

1. In an igniter plug, an insulator having a bore, a conductor in said bore, and means sealing 5 said bore around said conductor comprising a fused mass consisting of lead oxide and aluminum oxide and a second fused mass adjacent said first mass consisting of lead oxide and borosilicate glass.

2. A seal for a passage in a, high heat resistant material comprising a rigid mass consisting of a fused mixture of lead oxide and aluminum oxide and an adjacent mass consisting of lead oxide and a fusible substance having a melting point lower than that of aluminum oxide and higher than that of lead oxide.

3. A seal for a passage in a high heat resistant material, comprising a rigid mass consisting of a fused mixture of lead oxide and'borosilicate glass, and a second rigid mass adjacent said first mass consisting of lead oxide and a non-metallic substance having a melting point higher than that of borosilicate glass.

4. In a device of the class described, an insulator having a passage therein, a conductor in said passage, and means for sealing said passage around said conductor comprising two separate adjacent masses each consisting of a mixture of lead oxide and a non-metallic substance having a higher melting point than said oxide, and said substance in one of said masses having a higher melting point than said substance in the other mass.

5. A center electrode assembly for an igniter plug comprising an insulator having a bore therethrough, an electrode bar having a sliding fit in said bore and an integral collar intermediate its ends engaging a shoulder in an enlarged portion of said bore, a terminal extending into said enlarged ortion of the bore, a small wire electrically connecting said bar and terminal in said bore, a fused mixture of lead and aluminum oxides filling a portion of said enlarged bore around said bar and wire, and a fused mixture of lead oxide and borosilicate glass filling a portion of said enlarged bore around said wire and terminal.

6. In a device of the class described, a rigid tubular insulator having a stepped bore, a metallic bar having one end thereof closely fitting the smaller part of said bore, and a collar intermediate the ends thereof engaging the annular shoulder in said bore, a terminal extending into the larger part of said bore, an elongated conductor having a small transverse cross section electrically connecting said bar and terminal, a fused mixture of lead oxide and aluminum oxide filling a portion of said bore adjacent said collar around said bar and conductor, and a fused mixture of lead oxide and borosilicate glass filling said bore around the remainder of said conductor and a portion at least of said terminal.

7. A device of the class described comprising a metallic shell having a bore therethrough, a onepiece rigid tubular insulator in said bore, the inner and outer diameters of said insulator being stepped, the larger portion thereof being at one end and approximately fitting the shell bore and forming a well for receiving a readily removable terminal connector, means for detachably securing said terminal connector to said shell at one end thereof, means for mounting said insulator in said shell comprising a ring of relatively soft metal, such as copper, wedged between a reduced central cylindrical part of said insulator and a tapered portion of the bore of said shell and a fused flux interposed between the surface of said ring and the surfaces of said insulator and shell, the portion of said ring having the greatest wall thickness being remote from said larger portion of the insulator, conducting means having a reduced central portion extending through at least a portion of the bore of said insulator, sealing means around said reduced portion of the conducting means in said reduced central portion of the insulator including two masses, one con sisting of a fused mixture of lead oxide and aluminum oxide and the other of a fused mixture of lead oxide and borosilicate glass, and an electrode on the end of said shell remote from said securing means and in spark gap relation with the projecting end of said conducting means.

8. A device of the class described comprising a tubular metallic shell having a central portion of the bore therethrough tapered, a rigid tubular insulator in said bore having a stepped external diameter the larger portion thereof being only slightly smaller than the inside diameter of said shell and a smaller portion thereof being surrounded by said tapered portion of the bore, and a metallic ring wedged between said tapered portion of the bore and said insulator to support the latter in the shell, the portion of said ring having the greatest wall thickness being remote from the larger end of said insulator.

9. In a device of the class described, a metallic shell having a bore, a rigid insulator in said bore, and means for supporting said insulator in said shell comprising a ring of metal, such as copper, wedged between said shell and insulator and a fused flux interposed between said ring and said insulator, the quantity of said flux being insufficient to prevent intimate surface contact between said ring and insulator.

10. In a device of the class described, a metallic shell having a bore, a rigid insulator in said bore and means for supporting said insulator in said shell comprising a ring of metal, such as copper, wedged between said shell and insulator and a fused flux interposed between said ring and said shell, the quantity of said flux being insufficient to prevent intimate surface contact between said ring and shell.

11. In a device of the class described, a tubular insulator, a metallic ring surrounding and having intimate surface contact with a part of said insulator, and a fused flux between said ring and said insulator in an amount sufiicient only for filling the interstices of said surfaces and the voids therebetween.

12. An igniter plug comprising a metallic shell, a ground electrode at one end of said shell, a one-piece tubular insulator in said shell having an enlarged cup shaped portion at one end thereof approximately fitting the bore of said shell and forming a well for receiving a readily removable connector terminal, conducting means extending through said insulator from the bottom of said well to a point adjacent said electrode, and means for supporting said insulator in said shell comprising a ring of soft metal, such as copper, wedged between a central cylindrical portion of said insulator and a tapering portion of the bore of said shell, the portion of said ring having the greatest wall thickness being remote from the larger portion of said insulator.

13. The method which comprises the steps of loosely assembling a ring of metal coated with a flux between the inner surface of a metallic shell and the outer surface of a rigid insulator, said surfaces being convergent, and holding said shell and insulator against relative movement while applying heat and pressure to said ring for melting the flux and compressing the ring between said surfaces.

14. The method which comprises the steps of pressing a, soft metallic part between two stationary converging surfaces while the same are heated, and lubricating the contacting faces of said part and surfaces with a molten flux, said flux being applied as a thin powder coating and fused by the applied heat.

HARRY A. BRINSON. THOMAS G. BRADY.

References Cited in the file of this patent UNITED STATES PATENTS Number Number 8 Name Date 1 Thurneyssen Sept. 9, 1930 Lilienfeld Sept. 24, 1935 Hurley Nov. 8, 1938 Baier Oct. 8, 1940 McCarty June 24, 1941 Schwartzwalder et a1 July 8, 1941 Doran Feb. 23, 1943 Schwartzwalder Apr. 20, 1943 Hopps May 23, 1944 Tognola Aug. 15, 1944 

